2
THREE PHASE POLE MOUNTED DISTRIBUTION TRANSFORMER
INSTRUCTION
MANUAL #105
2. Lightning Arresters: Convenonal transformers should be
protected by properly rated lightning arresters. Ground
connecons on the arresters should be made before connecon
to the high voltage line is made.
CSP transformers are lightning protected by gapped or direct
connected lightning arresters bolted to mounng pads welded to
the tank wall. Gapped arresters have an adjustable electrode on
the top terminal of the arrester to obtain the proper gap seng
to the bushing electrode.
Before the transformer is put into service, the gap type arrester
electrode should be checked for proper gap alignment and
spacing. Adjustments should be made as necessary.
3. Secondary Breakers: ERMCO CSP and CP transformers are
protected against secondary overloads and short circuits by an
internally mounted circuit breaker. The funcon of the breaker is
to open the low voltage circuit and protect the transformer from
faults or severe overloads.
The breaker operang mechanism is designed to be operated by
a lineman's hot sck. Transformers are shipped with the circuit
breakers closed.
To open the low voltage manually, move the handle fully
counterclockwise so that the pointer moves from the "C" (closed)
to "O" (open), at which point the circuit is open. Verify that the
circuit breaker is latched in the "open" posion. To ensure the
discharge of the stac charge which is somemes present in the
low voltage winding due to capacitance, it is recommended that
the low voltage be grounded aer opening the circuit breaker
unl aer the high voltage is disconnected.
To close the breaker, rotate the handle fully counterclockwise to
"R" (reset), which engages the latch mechanism, and then
clockwise to "C" (closed). If a fault exists or an excessive load
exists at the me the breaker is closed, the breaker will reopen
even though the handle is held in the "C" (closed) posion.
Some breakers are provided with a red signal light which gives
warning that the load has reached a value near the tripping point
of the breaker. The signal light remains lighted unl reset (turned
off) by means of the breaker operang handle. Transformers
should not be operated under load condions that will cause the
red light to appear frequently, since it indicates an overload on
the transformer. When such a condion exists, it is
recommended that a larger transformer be substuted to avoid
impairing the life of the smaller unit.
To reset the signal light without disconnecng the load, rotate
the handle to "L" (light), and then return to "C" (closed). If the
light fails to go out, the transformer is sll overheated. To check
the signal light bulb when the transformer is in service, rotate the
handle to "L" (light). The light should turn on. If it does not, the
bulb should be replaced.
Some circuit breakers are equipped with an emergency overload
device which can be used to restore service following a circuit
breaker operaon due to overload. The emergency overload
lever is located immediately above the breaker operang handle.
With the emergency lever in the normal posion, the breaker will
trip at its normal seng as calibrated at the factory. Moving the
lever in a clockwise direcon increases the seng so a higher
temperature is required to trip the breaker. The emergency
seng may be adjusted to an intermediate or extreme value.
This emergency seng provides extra load capacity and sll
permits manual breaker operaon, and also retains short circuit
protecon of the transformer. It is important that the emergency
seng be used only when, and as long as, absolutely necessary
because its use will result in a reducon of transformer life.
A meter seal is provided on the emergency lever to prevent
tampering. It is recommended that a new seal be applied to the
lever when it is returned to the normal posion aer emergency
operaon.
The breaker is a thermal and short circuit protecve device for
the transformer. It is not recommended that the breaker be used
for roune disconnect operaons.
GASKETS
Cover and bushing gaskets are all made of Buna‐N Nitrile rubber.
Gaskets may be reused if not damaged. Round covers must seat
evenly on the gaskets so that pressure is distributed evenly. The cover
must be ghtened firmly to insure an effecve seal.
DUAL VOLTAGE AND TAPS
ERMCO transformers rated for more than one primary voltage are
equipped with a dual voltage switch or tap changer. These switches
are externally operated, but should never be operated while the
transformer is energized. When switching from one voltage to
another, make sure the switch is in the proper posion before re‐
energizing the transformer. Aer turning the switch, ghten the
locking device to minimize the possibility of unintenonal
movement.
STORAGE
Transformers should be stored filled with oil and in a clean dry place,
if possible where there will be no extreme temperature changes.
Before the transformer is put in service, it should be checked in the
same manner as when received.
ERMCO | 2225 Industrial Road | Dyersburg, TN 38024 | (800)238‐5587
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